Thermostat



F. J. HEIDEMAN.

THERMOSTAT.

APPLICATION FILED mAR.14. 1919.

Patenteti Apr. 13, 1920;,

UNITED STATES PATENT OFFICE.

FRED J. HEIDEMAN, OF DETROIT, MICHIGAN, ASSIGNOR, MESNE ASSIGNMENTS, TO

PERCY M. FOWL, HENRY R. KRUEGER, CHARLES E. FRENCH, AND FRED J. HEIDE- MAN, ALL OF DETROIT, MICHIGAN.

THERMOSTAT.

Application filed March 14, 1919.

a thermostat having a particular application to automatic refrigerating plants, although not limited to such application, Wl11Cl1 thermostat is arranged to open and close an electric switch upon a predetermined variation of temperature, and 1s quickly ad ustable to vary the extent to which the temperature must rise or fall to eifect a closing or opening of the switch.

Furthermore, it is an object of the invention to cause the opening or closing of the switch to take place upon a definite degree of movement of the thermostat regardless of any adjustment varying the responsiveness of the device to temperature conditions.

A preferred embodiment of the invention is illustrated in the accompanying drawing wherein:

Figure 1 is a vertical sectional view of the invention, a portion of the switch casing being omitted to disclose the mechanism of the switch.

Fig. 2 shows the thermostat in side elevation.

Fig. 3 is a top view of the thermostat.

Fig. 4: is a sectional View of a detail of the operating mechanism, the section being taken on line 4--it of Fig. 3.

In these views the reference characters 1- and 2 respectively designate the bottom and top plates of a frame or stand which carries the thermostatic mechanism, said plates being rigidly connected by bolts 3 passing through spacer sleeves 4, interposed between peripheral portions of said plates. These plates are of a spider construction, allowing a free circulation of air against the ends of the sylphon 5, arranged between said plates. and the bottom plate is formed with feet (3 adjacent its periphery to space it Specification of Letters Patent.

Patented Apr. 13, 1920.

Serial No. 282,549.

above any supporting surface, as for example a shelf within a refrigerator. The sylphon 5 is of the ordinary corrugated expansible tubular construction and is closed at its lower end by the plate 7 which is secured to the bottom member of the frame in any suitable manner.

The top surface of the plate 1 may be slightly recessed asindicated at 7 to allow said plate 7 to seat flush with the top of the plate 1. As a preferred means for holding the plates 1 and 7 in fixed relation there is employed a bushing 8 passing centrally through said plates and having on its upper end the annular flange 9 bearing upon the plate 7. The plate 1 is formed with a depending boss 10 to give more adequate retention to said bushing, the latter being rigidly held in said boss by any suitable means, as for example, welding. The upper end of the sylphon is closed by the plate 11, cupped or recessed in its center portion as is indicated at 12 in Fig. 1. The sylphon is supplied, as is usual, with some fluid having a relatively large coefficient of expansion, as for example, sulfur dioxid. The central opening 13 of the bushing 8 permits of filling the sylphon with the expansible liquid, said opening normally being sealed tween said nut and the upper end plate 11 of the sylphon there is engaged a coiled spring 17, the compression of which may be regulated by adjusting said nut. Above the nut 16 the post 15 intermediately engages a lever 18 which, upon being swungthrough a slight angle, is adapted to actuate a snap switch 19 to open or close an electric circuit 19*. The mechanism of said switch being. quite common is illustrated only in a general way, 20 and 21 being a pair of spring contacts, and 22 a contact pivoted between the members 20 and 21, and actuable by means of a reciprocatory rod 23 to either bridge the gap between the contacts 20 and 21 or to maintain the spaced relation to both of said contacts shown in Fig. 1, said mechanism being mounted within the two-part insulator casing 24, which is carried by the bracket 25 mounted fasgupon the plate 2.

To reciprocate the ro 23 through swinging of the lever 18, the latter is terminally formed with a yoke 26 which engages an annularly grooved collar 27 upon the lower end of said rod.

The fulcrum of the lever 18 is indicated at i mounting being such as to allow the fulcrum I to move vertically with the nut without rotating therewith. Thus the lever is fulcrumed upon the head portion of a screw 28 laterally projecting from the cylindrical support 29 slidably mounted in the slotted sleeve 30 carried by an arm 31 rojecting from the bracket 25. Through t e slot 32. of said sleeve the screw 28 projects. The lower end portion of the mem er 29 is engaged by the adjusting screw 33 which has. its head 1 3 1 disposed within an annular roove 35 jointly formed by the nut 16 an by a ring .36 screw-threaded upon said nut. A collar upon the screw 33 for adjusting the same is indicated at 37.

Discussing briefly the operation of the above-described device, it is evident that expansion of the sylphon is resisted by the coiled spring 17 and that expansion or contraction of the sylphon through a predeter-- mined extent will act upon the switch 19 to make or break the circuit 19.

The necessary degree of expansion or contraction of the thermostatto effect a snap actuation of the switch will. take place upon a relatively slight variation in temperature if the spring is under slight compression, any

increase in the degree of compression of the spring resulting in acorresponding increase in the temperature range, at the limits of which the switch is actuated. Thus'regin lation of the compression of the spring 17 by means of the nut 16 afi'ords an accurate control of the thermostat with respect to the temperature limits at which opening or closing of the electric circuit 19 takes place. By mountin the fulcrum of the lever 18 upon the ad usting nut, any inaccuracy due to shiftin of the switch rod 23 u n ad'ustment of t e nut 16 is substantial y avoided.

However in case any slight shifting of said rod should occur, owing perhaps to a shortening or lengthening of the spring 17 upon adjustment of the nut 16, the screw 33 may be turned to shift the lever fulcrum slightly up or down so as to return the rod 23 to its proper normal position.

Circuit closing means other than that shown might of course be similarly controlled by the disclosed thermostatic mechanism, and the other feature of the invention might be variously modified within the scope of the accompanying claims.

What I claim. is:

1. In a thermostat, the combination with the heat-responsive element thereof, of an electric switch, a lever for actuating said switch from the heat-responsive element, a

spring opposing expansion of the heat-re sponsive member, an abutment for said spring adjustable to vary the compression thereof, a fulcrum for said lever, and means constraining said fulcrum to follow said abutment when the latter is adjusted.

2. In a thermostat, the combination with the heat-responsive element thereof, of an electric switch, a lever for actuating said 1 switch, a rod for actuating the lever from said heat-responsive element, a spring opposing expansion of the heat-responsive element, an abutment for said sprin adjustable to vary the compression ther eo said abutment forming a slide bearing for said rod, a fulcrum for said lever, and means constraining said fulcrum to follow said abutment when the latter is adjusted.

' 3. In a thermostat, the combination with the heat-responsive element thereof, of an electric switch, a lever for actuating said switch from the heat-responsive element, a springopposing expansion of the heat-re: sponsive element, an abutment for said spring adjustable to and from the heat-responsive element to vary the compression of the spring, a fulcrum for said lever constrained to follow said abutment when the latteris adjusted, and means for adjusting said fulcrum with relation to the abutment.

4. In athermostat, the combination with a frame comprisin spaced plates,. of a sylphon arranged tween said plates, a bushing securing one end of the sylphon to one of said plates of the frame, the passage in said bushing forminga fill o enlng for the sylphon, a valve seated in said bushing normally closing the opening thereof, a switch carried by the other plate of said frame, and means for actuating said switch from the sylphon. I

In testimony whereof I sign this specification.

FRED J. HEIDEMAN. 

